unifi-mdns-discovery

unifi-mdns-discovery is a skill for Claude Code from mikeholownych/unifi-mcp. It costs 84 tokens per session (811 once invoked), scanned A, original, MIT.

A troubleshooting guide for finding devices across separate network sections. A VLAN is a separate logical network, and mDNS is the local discovery system used by products such as AirPrint, AirPlay, Chromecast, Sonos, and Spotify Connect.

In plain words
What is it for?
Use it when printers, speakers, TVs, or casting devices disappear after network segmentation, or when configuring multicast, IGMP snooping, mDNS forwarding, and firewall access.
Why use it?
Devices can still work while their apps cannot find them because discovery messages usually do not cross VLANs. The guide separates discovery problems from the later connection between the devices.

Skill for Claude Code

Written for Claude Code: argument-hint in frontmatter.

Good fit Use it when printers, speakers, TVs, or casting devices disappear after network segmentation, or when configuring multicast, IGMP snooping, mDNS forwarding, and firewall access.

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Install with agentmods
npx agentmods add skills/mikeholownych/unifi-mcp/unifi-mdns-discovery
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add mikeholownych/unifi-mcp --skill unifi-mdns-discovery
Clone the repo
git clone --depth 1 https://github.com/mikeholownych/unifi-mcp

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for unifi-mdns-discovery

README.md
[![agentmods](https://agentmods.dev/badge/skills/mikeholownych/unifi-mcp/unifi-mdns-discovery/github.svg)](https://agentmods.dev/skills/mikeholownych/unifi-mcp/unifi-mdns-discovery)
Your own site
<a href="https://agentmods.dev/skills/mikeholownych/unifi-mcp/unifi-mdns-discovery"><img src="https://agentmods.dev/badge/skills/mikeholownych/unifi-mcp/unifi-mdns-discovery/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for unifi-mdns-discovery

Your own site · 80×15
<a href="https://agentmods.dev/skills/mikeholownych/unifi-mcp/unifi-mdns-discovery"><img src="https://agentmods.dev/badge/skills/mikeholownych/unifi-mcp/unifi-mdns-discovery.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 84 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 811 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00084 $0.00811
Opus 5 $0.00042 $0.00405
Sonnet 5 $0.00017 $0.00162
Haiku 4.5 $0.00008 $0.00081

Measured 12d ago against content hash d3d21183f6e3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

unifi-mdns-discovery scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/unifi-mdns-discovery/SKILL.md · 61 lines

How it starts

The opening of the file, as written. The whole thing — 61 lines — stays where its author put it; the contents beside it link to each section on GitHub.

UniFi mDNS / Cross-VLAN Discovery

Fix "device works but apps can't find it" — the classic symptom of services that advertise via mDNS (Bonjour/Avataar/Cast/Spotify-Connect) being separated from their clients by VLANs or firewall zones.

Mental model

  • Discovery = link-local multicast to 224.0.0.251:5353. Routers do not forward multicast between subnets by design.
  • After the advert is discovered, the actual session is normal unicast — so the fix must carry the ADVERTISEMENTS across, and zone-firewall rules must allow the unicast session both ways (or rely on return traffic).

Step 0 & triage ladder

get_sysinfo (version facts are 10.x). Then:

  1. Same subnet first — put the phone ONTO THE SAME SSID as the device and retry. If it works there, it's a cross-VLAN problem → continue. This solves ~half of all cases instantly.
  2. Confirm both endpoints' networks: get_client_details for each (which SSID/network/VLAN). Watch for: phone on guest network, IoT on an IoT VLAN, client-isolation enabled on a guest WLAN (get_wlans: is_guest / l2_isolation) which blocks peer-to-peer even locally.
  3. Check WLAN multicast enhancement: get_wlans summary + underlying config — mcastenhance_enabled:true can suppress bonjour on that SSID. Disable per-SSID if discovery dies only on WiFi, not wired.
  4. Zone-firewall path (get_firewall_policies): look for existing Allow mDNS policies (udp) between the two zones. UniFi's mDNS repeater/ proxy typically handles reflection once permitted; if absent, plan:
    • ALLOW udp 5353 src= dst= (+ return), OR
    • enable controller mDNS proxy rather than raw firewall holes when available.
  5. IPTV caution: if the site has ISP IPTV multicast (look for "Allow IPTV Streaming" predefined policies / BELL-TV style zones), do NOT enable broad IGMP flooding/snooping changes globally — you can break live TV. Scope changes narrowly.

Common resolutions mapped to causes

Read the full file on GitHub · 61 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 12d ago First seen · 61 lines · 0 tokens per session scan A d3d21183f6e3

Subscribe to this mod's changes

unifi-mdns-discovery is a skill published in the GitHub repository mikeholownych/unifi-mcp (0 stars, last pushed 12d ago), licensed MIT. It adds 84 tokens to every session and 811 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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